Practical research and commercial applications of biotechnologies are expanding rapidly. The increasing utilization of biotechnology is evident in the areas of clinical research, general medicine, agriculture, chemical synthesis, and waste disposal, to name only a few. In an effort to identify potential occupational health hazards during the early stages of this development, the National Institute for Occupational Safety and Health conducted industrial hygiene surveys at six companies involved in research and development of recombinant DNA (rDNA) techniques applicable to fermentation processes. During each visit potential worker exposures, engineering controls, work practices, and medical surveillance programs were assessed. Varying degrees of proficiency and sophistication were noted in all of the assessed areas. Three companies new to the field (less than ten years old) of industrial fermentation were less sophisticated in their approach to issues involving occupational safety and health than were companies with years of experience (20, 25, and 106 years) in such operations. The three less experienced companies had no operational protocols, conducted limited (if any) environmental monitoring for chemical and microbial hazards, did not conduct preventive maintenance, and had very limited medical surveillance programs. Two of these companies had not conducted any environmental monitoring of the fermentation or product extraction processes. Recommendations were made in the areas of preventive maintenance, environmental monitoring, medical surveillance, and improved containment during fermenter inoculation.